International tensions over access to Covid-19 vaccines have intensified as supply hiccups disrupt mass rollouts of shots. But trade experts warn that restrictions on vaccine exports risk making a bad situation worse. That’s because the world’s major vaccine producers rely on each other for the essential ingredients to manufacture vaccines through a web of cross-border supply chains in complex chemicals, fatty acids and glass vials. If governments restrict vaccine exports, they risk retaliation from other members of this exclusive club of vaccine makers, who could withhold vital supplies, squeezing production just when it is needed most.

These supply chains stretch across the world, drawing in producers of basic chemicals that provide critical ingredients as well as the pharmaceutical powerhouses that make the vaccines. The  U.S. , the  European Union  and  China  are among a handful of territories that produce vaccine ingredients and final vaccines for the entire world. More than half of global vaccines and of key vaccine ingredients come from the  U.S.  and  EU . These 12 countries and the EU make up the “Vaccine Club”—producers that make both the key ingredients as well as final vaccines

The members of the vaccine club, though, source on average 88.3% of the imported ingredients used in vaccine production from other club members, according to economists led by Simon Evenett, professor of international trade and economic development at the University of St. Gallen in Switzerland, who have mapped trade flows between the world’s major vaccine producers. Limiting vaccine exports to another major producer would therefore risk retaliatory action that could undermine production, threatening the mass vaccination drives that are the key to ending the pandemic, Prof. Evenett said. “Everyone has a gun to each other’s heads,” he said.

Excerpts from The Covid-19 Vaccine Club: How the World’s Biggest Producers Depend on Each Other, WSJ, May 1, 2021